In general, fluoroalkenes are very useful compounds having many applications. For example, fluorinated alkenes such as 3,3,3-trifluoropropene (CF3CH═CH2) are useful as monomers for the manufacture of polymers (for example, fluorosilicones) and starting materials in the production of fluorinated chemical intermediates such as trifluoropropene epoxide and 3,3,3-trifluoropropylbenzene. Fluorinated alkenes are also used as aerosol propellants and as refrigerants.
Fluorinated alkenes such as, for example, 3,3,3-trifluoropropene, however, typically are made in multi-step processes. For example, carbon tetrachloride (CCl4) is typically added to ethylene to produce 1-chloro-3,3,3-trifluoropropane (CCl3CH2CH2Cl). A. L. Henne, et al, J. Am. Chem. Soc., 72 (1950) 3369, for example, teaches that fluorination of the latter using a CCl3CH2CH2Cl liquid phase fluorination process, such as HF in conjunction with an antimony catalyst, provides l-chloro-3,3,3-trifluoropropane (CF3CH2CH2Cl) which is subsequently dehydrochlorinated to yield 3,3,3-trifluoropropene. Alternatively, German Patent 1 140 928 teaches that CCl3CH2CH2Cl can be fluorinated in a vapor phase process to yield 3,3,3-trifluoropropene.
U.S. Pat. No. 5,986,151 also describes a multi-step process for making 3,3,3-trifluoropropene. In U.S. Pat. No. 5,986,151, the first step of the process requires the dehydrofluorination of 1,1,1,3,3-pentafluoropropane (CF3CH2CHF2; HFC-245fa) to 1,3,3,3-tetrafluoropropene (CF3CH═CHF) (HFC 1234ze). In the next step, 1,3,3,3-tetrafluoropropene (CF3CH═CHF) is reduced to 1,3,3,3-tetrafluoropropane (CF3CH2CH2F) by reacting a stream of gaseous 1,3,3,3-tetrafluoropropene (CF3CH═CHF) and hydrogen gas under catalytic conditions at suitable reaction temperatures. Finally, the 1,3,3,3-tetrafluoropropane (CF3CH2CH2F) is dehydrofluorinated to yield 3,3,3-trifluoropropene.
Other methods for producing fluoroalkenes include the use of hazardous reagents. U.S. Pat. No. 6,211,421, for example, describes the preparation of 1,1,1-trifluoropropene by liquid phase fluorination of 1,1,3-trichloroprop-1-ene with HF. U.S. Pat. No. 4,582,921 describes the reaction of vinylbromide with in situ generated trifluoromethylorganometallic reagents to yield 3,3,3-trifluoropropene (CF3CH═CH2). U.S. Pat. No. 4,220,608 describes fluorination of CCl3CH2CH2Cl or CCl3CH═CCl2 with HF in the presence of an amine to yield 3,3,3-trifluoropropene (CF3CH═CH2). In yet another publication, Organometallics, 19(5), 944–946, 2000, 3,3,3-trifluoropropene (CF3CH═CH2) is obtained via thermal conversion of trifluoromethyl oxirane with only a 32% yield.
As can be seen from the above description, many prior processes involve the use and/or production of chlorinated alkenes. Applicants have come to appreciate, therefore, that many of these processes result in the generation of one or more unwanted waste streams containing chlorinated products. As is known, chlorinated compounds are generally considered to be problematic from an environmental standpoint. For example, chlorinated hydrocarbons are frequently identified with environmental problems such as ozone depletion and global warming. Heretofore, these unwanted waste streams typically were disposed of by incineration, which itself is frequently considered environmentally unfriendly as well as economically inefficient.
The above processes also generally suffer from other drawbacks. These include the use of expensive or hazardous starting materials and/or the use of reagents and/or starting materials that need to be prepared in multiple steps. Another drawback of many prior processes is that the conversion of starting materials to the desired product such as, for example, CF3CH═CH2, involves multiple steps that make such processes less cost effective than is desirable for many commercial purposes. Moreover, certain prior processes require one or more dehydrohalogenation steps, and it is not uncommon that a significant amount of waste is produced as a result of such steps.
In view of the above and other failures of the prior art, applicants have come to appreciate a need for new processes for manufacturing fluorinated alkenes such as, for example, 3,3,3-trifluoropropene, particularly but not exclusively processes that use readily available starting materials, and/or that are more cost effective than certain prior processes, and/or that reduce the need to dispose of environmentally unfriendly waste products.